Each federal electoral district returns one Member of Parliament (MP) to the House of Commons of Canada; each provincial or territorial electoral district returns one representative — called, depending on the province or territory, Member of the Legislative Assembly (MLA), Member of the National Assembly (MNA), Member of Provincial Parliament (MPP) or Member of the House of Assembly (MHA) — to the provincial or territorial legislature.
While electoral districts in Canada are now exclusively single-member districts, multiple-member districts have been used at the federal and provincial levels. Alberta has had a few districts that returned from two to seven members: see Calgary, Edmonton and Medicine Hat. British Columbia had a mix of multiple-member districts and single-member districts until the 1991 election, and Prince Edward Island had dual-member districts until the 1996 election.
Since 2015 there have been 338 federal electoral districts in Canada. Ontario uses the same boundaries for the electoral districts for its Legislative Assembly in Southern Ontario, while seats in Northern Ontario correspond to the federal districts that were in place before the 2004 adjustment. The other provinces use different electoral districts for their legislatures. Ontario had separate provincial electoral districts prior to 1999.
Originally, most electoral districts were equivalent to the counties used for local government, hence the French unofficial term comté. However, it became common, especially in Ontario, to divide counties with sufficient population into multiple electoral divisions. The Constitution Act, 1867, which created the electoral map for Ontario for the first general election, used the term "ridings" to describe districts which were sub-divisions of counties. The word "riding," from Old English *þriðing "one-third" (compare farthing, literally "one-fourth"), is an English term denoting a sub-division of a county.